Safety shutter for projectors



June 1944- M. R. HUTCHIQSON, JR 2,350,761

SAFETY SHUTTER FOR PROJECTORS Filed July 16. 1942 4 i i MILLER RHUTCHISQVJR.

Z INVENTOR ""IIIIII/ y b a I W/Zwa A TTORNE YS Patented June 6, 1944 ssrurr SHUTTER FOR Pnomo'rons Miller B. Hutchison, Jr., Rochester, N. Y., as signor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey I Application July 16, 1942, Serial No. 451,143

'7 Claims. (01. 88-+24) This invention relates to safety devices for still or motion picture projectors. One object of my inventionis to provide a projector with a device which prevents film to be projected from be coming overheated. Another object of my invention is to provide a simple and inexpensive device which will permit light rays to pass to the film, or slide, in position for projection only when a cooling system is in operation. Still another object of my invention is to provide a device oi the type described in which there is no mechanical linkage for operating the safety device. Other ject wi ppe r from the followin specification, the novel features being particularly pointed out in the claims at the end thereof.

Projection apparatus ,-particularly where high powered lamps are employed, have usually been provided with some mechanical means for preventing a light beam from passing through the film or slide being projected except at such times as when a cooling system is in operation. Usually these devices are comparatively complicated and require mechanical operating connections of some sort sometimes depending upon speed governors or like devices. While many of these so-called safety shutters have worked satisfactorily, they are usually quite expensive and not particularly suitable for inexpensive apparatus.

My present device has largely liminated expensive parts and reduced the cost of a safety shutt t a More ver, it i simp in construction and requires no complicated as-. sembling operations so that it may readily be assembled by unskilled help. V

Coming now to the drawing wherein like reference characters denote like parts throughout;

Fig, l is a fragmentary plan view of an inela-v pensive type of motion picture projector constructedin accordance with and embodying a preferred form of my invention; 1

Fig, 2 is alongitudinal section taken on line 2-2 through the machine shown in Fig. 1;

Fig. 3 is a view showing the safety cap in position to pass light rays through an optical system; and

Fig. 4 is a transverse section taken on lin die-4 of Fig. 1 through the safety cap and lamphouse showing the safety shutter in'an operative or light blocking position.

My invention comprise placing a metallic cap over a lamp so t t th can h s a sl ding fit there: with anddirecting air from a blower aboutthe lamp in su h a ma n r t at t di ference in pressure caused y e blower t een the top nd t e o om of he lampmev use the can.

to rise to a position in which the bottom- 0f. the cap moves away from the lamp filament so t hat light rays may pass through an optical system and through a film. or slide im osition for pro: jection. 1 I

It is obvious that my. invention is suitabl for any piece of projection apparatus employing-a lamp and a cooling system, whether this apparatus is designedto utilize film, such as-motion picture film, slides or the l keflr SSi S d s; and is suitable for use in anycase with such a projector Where it is desired'to reduce the heat p sing through thefilm or'slide to a minimuml Thus, my improved heat. shutter will openly/hen the coolin a r e es p edet m ned quantity and will close when the blower output is-reduced or when the blower is turned off.- 7 .i 1

More specifically; my invention may-comprises projector or casing l oi anyrdesired -shapes eluding a filmgate 2 in whiclra filml? mat s in an optical system which, inrthis instance,.-rnay comprise-a condenser lens 3, a reflector 4, and. an objective carried by a focusing lensmounti. 1.2111 the present instance this. optical system-"isfa-r; ranged along an axis A which lies in a str'aight line, although of-cours if desired, mirrors-may be introduced into the systemfor changing the axis. v r.

I also provideon the axis A a lamp 6 having the usual type of filament 1, this lamp haying ah'ase 8 which ma be supportedin a known typet-of Socket h s lampfiand its socket 9. m ybe supported on-one wall [0 of a lamphousewhich may include an end wall ll, a top wall l2,.and an outside wall l3 having openings I through which air may pass. There are a pair of-parallel 20 is provided with a skirt? l ofrsuch a lengththat v when the capflli strikeslthe topwall 2,? for the projector. casing L-thev skirt ;.Wi 1l b in the pos tion.

shown in ig: 3 in -whichfhe lamp filamentsl are exposed. sch-that .ligh r ys ma assthrollsh the optical -system. .and,;through a. or slide located. in e mig'atel'rHowevsaLWhel 't e an 20 fully t lescopes he lamp-6 t askirt' wi lexten into the position shown in his-g4;

. l3 of the projector.

which it eifectively prevents light rays from passing from the filament I along the axis A to the film gate 2. Thus, it is only when the cap is in its raised position that light is effective at the film gate 2.

The blower member l8 consists of a fan having blades 28 carried by a shaft 29, which shaft may be operated by a motor M. The speed of this motor is such that the Ian 28 will create an air pressure about the throat l9 of the lamp which is considerably higher than the air pressure around the top of the lamp, since most of the air may escape through the openings M in the end wall However,;some of the air may pass out through the opening 30 in the top wall l2 which is preferably only of a size to permit the cap 20 to slide freely .therethrough.

When the motor M starts to drive the fan blades 28, the motor only slowly gets up to speed so that at first there is comparativel little difference in pressure at the two ends of the cap 20. However, as the speed increases and the'blower l8 operatesfat its maximum speed the pressure difierential is sufllcient to cause the cap to move from its Fig. 4 position to its Fig. 3 position since, of course, the pressure inside of the cap is substantiallythepressure at the throat l9 of the lamphouse and since it naturally moves toward a low pressurearea-near thetop of the lamp; Thus; the velocity of the air from the blower I8 is sufllcient to move the cap and, when themotor is reduced in speed or turnedofl, this'pressure differential is altered so lthat'cap 20 1s permitted to slide back a ain into its ,(Fig. 4) telescoping position, in which it blocks on light, being ,moved bygravity. "I, j f

The sliding fit between the cap 20 andlamp 6 is not critical butit is desirableto have th skirt 2l-fit rather closely the cylindrical wall 36 of the lamp 6 becauseI have found that if there is much clearance between these parts the cap is inclined to flutter or rattle against the lamp 6 and thus produce an, undesirable noise. However, where there isafreemovingtfit between the skirt 2| and the wall 36 o1'the lamp, the cap may move silently to and from its operative light blocking position, and in addition it will be held up against the top wall 22 of the projector casing during all of that time iirwhich the blower 18, is operating atitsproperspeed, Y

In the present embodiment of my inventionI have shown the projector to bee, motion picture projector and the film I may be intermittently movedthroughthe film gate 2 by means: of a pull dpwn mechanism diagrammatically shown at 40, which may be, operated fromthe shaft 4| turned by 'a gear ,42 which may also constitute a shutter. This .gear 42 turns a worm wheel 43 the fan varies and, consequently, the film is moving at the standard speed before the fan can move air with sufiicient, velocity to raise the safety shutte or cap to a position in which light passes from the filament l to the reflector 4 and through the condenser lens 3 and the film gate 2.

-If the'projector is for projecting slides such as: slides madev on a cellulosic .base alone or film slides mounted on one glass plate or between two glass plates, it is not necessary to consider movement of the slide because it remains stationary during exposure. However, in such cases it is desirable to have the air for cooling the lamp 6 reacha cooling velocity to carry off undue heat before the slides are exposed, so that in such an instance it. is still desirable to have a cap which will serve as a safety shutter and which may be moved by differential air pressure upon the operati n of the l w rt t 7 It shouldbe noted that eithe'r amotio n picmm 'or still'projecto'r does not have the move ment of the air stream materially interfered with by the addition of my safety shutter lamp cap. The beneficial safety results are obtained without a-sacrifice of the usual cooling air stream which isnevertheless used to operate the safety shutter.

While I have described a preferred embodiment of my invention it is obvious that various embodiments can readily'be devised in accordance wlthmy invention and I consider as within the scope thereof all such embodiments as may come within thescope of the appended claims.

I claim} e 1. A safety shutter for motion picture projectors of; the"type including an objective, a film gate and-a am for illuminating the film gate, the combination with said lamp,- of a housing for directing airabout' the lamp including a restricted area'about the bottom of the lamp, a blower for supplying air to the housing through the restricted area, and-a cap' carried bythe lamp and having a sliding fit therewith of a length to prevent illumination from reaching the gate when contacting withthe top of the lamp and adapted to be raised'to illuminate the film gate when air from the blower passes about the lamp and cap,

. a stop carried by the projector for limiting upward m'ovement of the cap. a

2'. A safety shutter for motion picture projectors of the type including an objective, a' film gate and a lamp for illuminating the film gate,

the combination with said lamp, of a housing for and worm 4! whichin turn operates a" shaft carrying a sprocket 46 which "moves a film to and from the filmgate 2 in a'known manneni' It is obvious that with a machine of this type it is not desirable topass. light rays to the'film;

F in the gate 2 until the machine gets up to at gear 48 meshing with the gearfllg ('Jonsequently,

with this tembodimentiof m'y ir 1ventio'n the speed of the film varies when the speed of 7 directing air about the lamp including a restricte'darea about the bottom of the lamp, a blower for supplying air to the housing through the restricted area, and a 'cap carried by the lamp and having a sliding fit therewith of a length to prevent illumination from'reaching the gate when contacting with the top of the lamp and adapted to be raised to illuminate the film" gate' when air from the blower passesabout the lamp and cap. and means included in the casing for limiting the upward movement of the cap to a position in which parts ofthe cap remain in contact with saidlamp; Y t

3. A safety shutter'for motion picture projec:

\ tors of the type including an objective, a fiim gate and a lampfor illuminating thefilm gate, the combination with said lamp, of a housing for directing air about the, lamp including a restricted; area'about' the bottom of the'lamp, a blower for supplying air to the housing; at varying velocities through the restricted area, a cap of a shape closely approximating the shape of the top of the lamp and having a freely sliding fit thereon, said cap including a skirt of such a length as to prevent illumination of the film gate, said cap being slidable on the lamp to a position in which the skirt may move to a position in which the film gate may be illuminated, the sole means for moving the cap comprising air moved by the blower through the housing and around the lamp.

4. A safety shutter for motion picture projectors of the type including a lamp house, an objective, a film gate and a lamp of substantially cylindrical shape and having a rounded end and a filament inside the lamp for illuminating a film gate, the combination with said lamp, of a safety shutter comprising a cap slidably fitting said lamp and including a rounded top and skirt encircling the cylindrical part of said lamp a distance sufiicient to cover said filament and block off light to said film gate, a blower, means directing air about said lamp from the blower, and including a restricted area around the lower part of the lamp, said blower by delivering air about the lamp through the restricted area being adapted to lift the cap until said skirt is moved from its light blocking position whereby light may pass from the filament to the film gate, said cap descending to a light blocking position when the,

air from the blower is insufficient to hold said cap in a raised position.

5. A safety shutter for motion picture projectors of the type including a lamp house, an objective, a film gate and a lamp of substantially cylindrical shape and having a rounded end and a filament inside the lamp for illuminating a film gate, the combination with said lamp, of a safety shutter comprising a cap slidably fitting said lamp and including a rounded top and skirt encircling the cylindrical part of said lamp a distance suflicient to cover said filament and block off light to said film gate, a blower, means directing air upwardly about said lamp from the blower, and including a restricted area aroundthe lower part of the lamp, said blower by deliver.

ing air about the lamp and through the restricted area being adapted to lift the cap until said skirt is moved from its light blocking position whereby light may pass from the filament to the film gate, a stop for limiting the movement of the cap on the lamp under the impulse of the air blast whereby at least a portion of said cap may always remain about the lamp.

6. A safety shutter for projectors of thetype including a lamp house, a film gate, an optical system passing through the film gate, and a projection lamp mounted in the lamp house, the combination with said lamp, of a cap telescopically fitting said lamp and slidably mounted thereon, a stop limiting upward movement of the cap for keeping at least a portion of the cap encircling the lamp, a blower, means for directing air from the blower to the lamp so shaped as to produce a difference in air pressure between the top and bottom of the lamp when the blower is operatin said cap moving to and from an operative light blocking position in accordance with pressure changes about the lamp.

7. A safety shutter for projectors of the type including a lamp house, a film gate, an optical system passing through the film gate, and a projection lamp, the combination with said lamp, of

a cap telescopically fitting said lamp and slidably mounted thereon, an open passageway in the top wall of said housing about the top of said lamp, a blower, means for directing air from the'blower to the lamp so shaped as to produce a difference in air pressure between the top and bottom of the lamp when the blower is operating, said means including an air passageway from the blower to the lamp, a restricted throat in the passageway about the lower part of the lamp forming a high pressure area, said open passageway about the top of the lamp forming a low pressure area whereby said cap may move from the high to the low pressure area when the blower is operating.

MILLER, R. HUTCHISON, JR. 

